Cisco CCNA Exam Tutorial IGRP And Equal Cost Load Balancing
Below is a MRR and PLR article in category Computers Technology -> subcategory Computer Certification.
Cisco CCNA Exam Guide: Understanding IGRP and Equal Cost Load Balancing
Summary:
This guide will help you master configuring equal cost load balancing for your CCNA exam. Let's explore IGRP and EIGRP with insights from Chris Bryant, CCIE
12933.
---
To successfully pass the CCNA exam, understanding how to use the bandwidth command with IGRP and EIGRP is crucial. This tutorial will guide you through configuring IGRP over a frame relay hub-and-spoke network using the following setup:
Network Configuration:
- R1 (the hub), R2, and R3 are connected via IGRP over the 172.12.123.0/24 network using a T1 line.
- R1 and R3 are also linked by a subnet, 172.12.13.0/24, with a bandwidth of 512 KBPS.
- Additionally, R2 and R3 communicate over an Ethernet segment, 172.23.0.0/16.
Steps to Configure IGRP:
We'll use the `router igrp 1` command to implement IGRP on R1, R2, and R3 across networks 172.12.0.0 and 172.23.0.0.
On R1:
```plaintextR1
conf t
R1(config)router igrp 1
R1(config-router)network 172.12.0.0
```On R2 and R3:
```plaintextR2
conf t
R2(config-if)router igrp 1
R2(config-router)network 172.12.0.0
R2(config-router)network 172.23.0.0
R3
conf t
R3(config-if)router igrp 1
R3(config-router)network 172.12.0.0
R3(config-router)network 172.23.0.0
```IGRP Routing Overview:
Upon running `show ip route` on R1, you’ll observe three equal-cost paths to the Ethernet network. IGRP naturally supports load-sharing over up to four equal-cost paths, and all these paths will be visible in the routing table. Additionally, you'll find routes to the loopback addresses on both R2 and R3. To filter for IGRP routes, use `show ip route igrp`.
```plaintext
R1
show ip route igrp
```Routing Details:
```plaintext
I 172.23.0.0/16 [100/8576] via 172.12.123.2, Serial0
[100/8576] via 172.12.13.3, Serial1
[100/8576] via 172.12.123.3, Serial0
```
Note: The brackets indicate the Administrative Distance and the IGRP metric. As a classful protocol, IGRP doesn't support VLSM.
Modifying Bandwidth Perceptions:
To correct IGRP’s assumption that both serial connections (R1 to R3) are T1 lines (1544 KBPS), we’ll adjust the bandwidth on the Serial1 interfaces to reflect the actual 512 KBPS.
On R1 and R3:
```plaintextR1
conf t
R1(config)interface serial1
R1(config-if)bandwidth 512
R3
conf t
R3(config)interface serial 1
R3(config-if)bandwidth 512
```This adjustment changes IGRP’s perceived bandwidth, not the actual line speed. Clear the routing table on R1 for changes to take effect.
```plaintext
R1
clear ip route *
R1show ip route igrp
```With this update, the route through the 172.12.13.0 network will no longer participate in equal-cost load balancing because it is now seen as slower.
In the next section, we’ll explore configuring unequal-cost load balancing.
---
You can find the original non-AI version of this article here: Cisco CCNA Exam Tutorial IGRP And Equal Cost Load Balancing.
You can browse and read all the articles for free. If you want to use them and get PLR and MRR rights, you need to buy the pack. Learn more about this pack of over 100 000 MRR and PLR articles.